Computer appliance comprising a multiway acoustic output and input system

ABSTRACT

According to the invention, at least one acoustic output is connected to at least one acoustic input of a computer appliance having a multiway acoustic output and input system. The acoustic signal that is guided via said connection is supplied to an acoustic echo canceller (F) as a reference signal for levelling with an acoustic signal which is supplied to the acoustic echo canceller (F) by means of at least one other multiway acoustic input which is connected to a microphone (M). Echo filtering is thus made possible in a personal computer because the supplied signals are always timely correlated with one another regardless of the delays in signal processing, whereby said delays are caused by the operating system. Echo filtering allows for handsfree talking when entering voice data.

[0001] The invention is directed to a computer appliance having amultipath acoustic output and input system according to the preamble ofclaim 1.

[0002] For example, telephone devices have means for eliminatingacoustic echo signals [ . . . ] known as acoustic echo eliminationcircuits and also referred to as Acoustic Echo Canceller (AEC) which arecoupled, by the receiver of the telephone device, through the space intothe speaking piece. [sic] The acoustic echo canceller is particularlyimportant when speech is uttered without holding an acoustic inputdevice to the ear and mouth.

[0003] An adaptive filter is a crucial component of the acoustic echocanceller. The adaptive filter reproduces the transmission function ofthe space. On one hand, the acoustic echo canceller receives, as areference signal, the output signal which is guided to the loudspeakerand, on the other hand, receives the input signal which is led into thesystem by the microphone. Therefore, the output signal follows twoseparate paths. One time, it is directly applied and, another time, itis guided via the loudspeaker through the space and the microphone. Ifthe filter is adapted effectively, both paths are equivalent. The twopaths are equivalent since the adaptive filter precisely reproduces thepath of the output signal via the loudspeaker, the space and themicrophone given an effective adaptation. Therefore, the difference ofthe two signals is at least almost zero. The suppression of the echo isthus achieved.

[0004] The echo can only be suppressed when the signal reaching theloudspeaker and the signal accepted by the microphone correlate in termsof time. In this context, a chronological correlation means that only aconstant delay is present between the two relevant signals. In additionto the generally known telephone devices, ever more computer appliances,such as personal computers, are used for telephoning. As mentionedabove, it is particularly important that an effective adaptation of theadaptive filter of the acoustic echo canceller is present since thesignal of the remote speaker can have an unimpeded effect on themicrophone given handsfree talking. Different from telephone devices, acomputer appliance has the disadvantage that the means for providingacoustic signals to be outputted and the means for processing receivedacoustic signals do not exhibit a constant delay over the course oftime. For different reasons caused by the operating system of thecomputer appliance, the delays are not constant with respect to thedistance via the loudspeaker, the space and the microphone. The signalsarriving at the acoustic echo canceller, i.e., the signal which isoutputted via the loudspeaker and the signal which is accepted by themicrophone, do not chronologically correlate with one another.Therefore, a onetime adjusted adaptation of the adaptive acoustic echocanceller is not sufficient in order to always suppress the echo.

[0005] On the basis of a computer appliance of the aforementioned type,an object of the invention is to provide technical measures which enablean adaptation of the filter of the acoustic echo canceller that isalways precise regardless of the chronological delays of the componentsof the computer appliance, whereby said chronological delays arevariable for acoustic signals.

[0006] This object is inventively achieved by the features of thecharacterizing part of claim 1.

[0007] Due to these features, the acoustic signals at the adaptivefilter of the acoustic echo canceller, namely the acoustic signal forthe receiver or, respectively, loudspeaker of the computer appliance andthe acoustic signal accepted by the microphone, are independent ofoccurring variations given the chronological delays of the componentsfor the acoustic signals always chronologically correlate with oneanother. [sic]

[0008] Advantageous embodiments of the invention are subject matter ofsublaims.

[0009] The invention is subsequently explained in greater detail on thebasis of a drawing. FIG. 1 shows a basic termination circuit of a filterof an acoustic echo canceller in a telephone arrangement according tothe prior art,

[0010]FIG. 2 shows a basic operational diagram of the output and inputof acoustic signals in a computer appliance according to the prior art,

[0011]FIG. 3 shows an operational diagram according to FIG. 3 with delayelements added in a basic manner,

[0012]FIG. 4 shows an operational diagram according to FIG. 4 with adetailed representation of an acoustic echo canceller according to FIG.1, and

[0013]FIG. 5 shows a basic operational diagram of the output and inputof acoustic signals in a computer appliance according to the invention.

[0014] The same elements have the same reference characters in theFigures.

[0015]FIG. 1. schematically shows an acoustic echo canceller whose coreis an adaptive filter F. An acoustic signal to be outputted, as ananalog electrical signal in the present case, is guided, via a line a,to an input of the filter F and to a loudspeaker L. The loudspeaker Ltransforms the analog electrical signal into an acoustic signal and saidsignal is radiated into a space R. A microphone M receives the acousticsignal and transforms it into an electrical analog signal. The analogsignal, via a line b, is guided to a positive input of a compoundcircuit S. An output signal of the filter F is led to a negative inputof the compound circuit S. For readjusting purposes, a result signal ofthe compound circuit S is led to a feedback input of the filter F.

[0016] The filter F is adjusted such that it balances the delay circuitfor a signal—which travels the distance from the line a via theloudspeaker L, the space R, the microphone M and the line b—to theextent that the signal at the input of the filter F arrives at the sametime at the compound circuit S as the signal led via said path. In thisway, an echo can be suppressed.

[0017] The system shown in FIG. 1 only has a constant delay, so that thesignals on the lines a and b are chronologically correlated.

[0018] In a complex system, such as a personal computer, the output andinput of audio signals occurs differently. FIG. 2 shows the part of apersonal computer which is crucial for an output and input of audiosignals. This part has first means M1 for digitally processing acousticsignals to be outputted or, respectively, acoustic signals that havebeen received. Furthermore, this part has second means M2 for editingpurposes for forwarding acoustic data provided by the first means M1 foran output or, respectively, for editing purposes for a forwarding to thefirst means M1 of the received acoustic data. [sic] Finally, this parthas third means M3 for converting the acoustic data, which are edited bythe second means M2 for the transfer, into analog acoustic signals andfor acoustically outputting the converted analog acoustic signals vialines a and the loudspeaker L in this case. The third means M3 are alsoused for the conversion for the second means M2 into digital acousticdata of analog acoustic signals accepted via the microphone M and vialines b in the present case. [sic]

[0019] In the concrete case, the first means M1 are at least partiallyformed by program control elements of the computer appliance that isrelevant in FIG. 2. The second means are formed by what are referred toas drivers which are necessary for operating specific device parts of acomputer appliance. The third means M3 imitate a what is referred to assound card. The sound card, in the one direction, converts digitalsignals into analog signals and, in the other direction, converts analogsignals into digital signals.

[0020] The loudspeaker L and the microphone are acoustic converters. Inthis sense, the loudspeaker L represents a first acoustic converter andthe microphone M represents a second acoustic converter, for example.

[0021] The circumstance that the arrangement of FIG. 2 has a number ofpaths to the loudspeaker or, respectively, a number of paths from themicrophone indicates that an output or, respectively, an acceptance ofaudio signals or, respectively, acoustic signals can occur separatelyfrom one another on a number of channels, as this is the case withrespect to stereo transmissions, for example. In this case, at least onefurther loudspeaker L or, respectively, one further microphone M areprovided.

[0022] In the present case, a stereo transmission or, respectively, astereo acceptance is not realized. Therefore, respectively one line aor, respectively, b is basically redundant for the output and also forthe acceptance of audio signals.

[0023] The transmission of signals from the first means M1 to the secondmeans M2 and from the second means M2 to the third means M3 or,respectively, from the third means M3 to the second means M2 and fromthe second means M2 to the first means M1 is respectively critical. Thistransmission is not possible without delays. The sizes [or: lengths] ofthe delays, among other things, are determined by the operating systemor, respectively, by the current situation of the operating system.

[0024] Therefore, FIG. 3 shows the system of FIG. 2 with delay elementsD1, D2. The delays shown by the delay elements D1, D2 are not constant,as it has been indicated above. As a result, the signals at theloudspeaker L and at the microphone M do not correlate in terms of time.Therefore, an acoustic echo canceller (see FIG. 4) formed by parts ofthe first means M1, at least, does not function satisfactorily.

[0025] This problem is solved by a connection of the present partsaccording to FIG. 5. At least one of the output multipaths is connectedto at least one of the input multipaths. In the present case, they areeven short-circuited. Furthermore, the means of the first means M1,which reproduce an acoustic echo canceller, are connected such thatthey, on the input side, have a connection with one of the inputmultipaths which has an executed connection with one of the outputmultipaths. Furthermore, these means are connected such that they, atthe output side, have a connection with an input multipath which has aconnection to a microphone M.

[0026] The acoustic echo canceller thus “reads” the channels of thesound card, whereby the signal of at least one microphone is situated inat least one of the channels and the reference signals therefor. Thissignal is the same signal which has also reached the loudspeaker. It ischronologically correlated with the signal of the microphone since theecho through the space (signal at the microphone) and the referencesignal for the filter traveled the same path through the sound card.

[0027] Although the delays symbolized by the delay elements D1, D2change, the echo signal and the reference signal for the filter alwaysremain chronologically correlated in this way. It is thus possible torealize an acoustic echo canceller in a personal computer.

[0028] If the sound card is fashioned such that it has at least onefurther audio output and audio input, which is not used for the audiooutput or, respectively, input, in addition to one or more audio outputsor, respectively, audio inputs, which are used for the audio output or,respectively, audio input, an acoustic echo canceller can besuccessfully used in the personal computer although a number of channelsare used in a personal computer for the audio output or, respectively,audio input.

1. Computer appliance having a multipath acoustic output system and amultipath acoustic input system, comprising first means for digitallyprocessing acoustic data to be outputted or, respectively, receivedacoustic data, second means for and editing for a forwarding of theacoustic data provided by the first means for an output or,respectively, for an editing for a forwarding to the first means of thereceived acoustic data, and third means for converting the acousticsignals, which are edited by the second means for the forwarding, intoanalog acoustic signals, and for acoustically outputting the convertedanalog acoustic signals via at least one single [sic] of the outputmultipaths and by at least one single first acoustic converter and forthe conversion for the second means into digital acoustic data by [sic]via at least one single of the input multipaths and the analog acousticsignals accepted by at least one single second acoustic converter,characterized in that at least one of the output multipaths is connectedto at least one of the input multipaths, and that the first means (M1)have means reproducing an acoustic echo elimination circuit (F), wherebysaid means, on the input side, are connected to the input multipath thatis connected to an output multipath and, on the output side, areconnected to an input multipath that is connected to a second acousticconverter (e.g. M).
 2. Computer appliance according to claim 1,characterized in that at least one of the connections between an outputmultipath and an input multipath is fashioned as a short-circuitconnection.
 3. Computer appliance according to claim 1 or 2,characterized in that the first means (M1) comprise elements of aprogram control, the second means (M2) comprise driver functions and thethird means (M3) comprise sound card functions.
 4. Computer applianceaccording to one of the claims 1 to 3, characterized in that the firstacoustic converters are formed by loudspeakers (L) and the secondacoustic converters are formed by microphones (M).